While attending Central High School he was befriended by veteran big band sideman Johnny Kopecky, under whom he studied both the double bass and violin.
After military service in an Army band near the close of World War II, Mosher returned to Sioux City where he landed a steady job as bassist in the house band led by tenor sax player Don Couch at the Turin Inn, a venerable Sioux City jazz club that regularly featured big name touring jazz artists—including the Bud Powell Trio.
While in Los Angeles with the Brown band, Mosher also performed some local LA club dates with both Zoot Sims and Chet Baker.
Mosher recorded with Graves on two sessions that became the LPs Genius at Work and VIP: Very Important Pianist, released on the Liberty label.
Mosher's bowed solos on several tracks of these sessions was a bold departure from the jazz norm of the time and was only paralleled by a then-up-and-coming Paul Chambers.